Speaker Compatibility Question - Scanspeak B741
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| Posted on November 15, 2020 at 02:04:05 | ||
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Posts: 1074
Location: Essex Joined: November 23, 2000 |
I've been asked to advise if a 300B SET amp could give good results with a Scanspeak B741 speaker; full details can be seen on the link. The amp is conventional 300B, no feedback, James OPTs, about 7 watts. As he is in Romania and I'm in the UK, shipping my amp two ways would be most costly even though I'd be willing to lend it; so some 'best guess' advice will be helpful. At first I was hopeful as sensitivity seems adequate. As a comparator, my main speakers are MTM with Seas ER18RNX drivers, 6.5 inch, somewhat similar to the bass drivers of the B741 and of similar sensitivity. These speakers are fine with a 300B SET and even better with my 45 PSE of 3.5 watts, suggesting the 300B amp would have enough power for the B741. However, the impedance of the B741 in the midrange is a concern raised by the guy, as it drop to 2.8 ohm. The amp does have a 4 ohm tap but I guess its Zout would be close to the 2.8 ohm, and could affect the midrange frequency response. In the case of my own MTM, as it is a 2 way speaker (made by me) I could model the effect of Zout and adjust the crossover in this way and by SPL measurement and by ear. But I would not have the foggiest idea how to do this on the complex crossover of the B741. My gut feel is that a push/pull valve amp, say EL34, would be a better match; EL34 PP in triode mode can give a degree of triode sound in my experience and sound good. I tend to recommend this to the guy. I have of course googled these speakers and found one reference suggesting a low power valve amp would not be suitable. I know it's a difficult question but advice is welcomed.
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